With the evolvement of the radio network communication technology, from the second generation Global System for Mobile communication (GSM) to the third generation Wideband Code Division Multiple Access (WCDMA) system, then to the third Enhanced Universal Radio Access (E-UTRA) system, according to users' demands, multiple systems coexist in the network deployment of operators. At present, the radio network functions of the operators are usually provided like this: the second generation GSM system is mainly used for carrying the voice; the third generation WCDMA system is mainly used for carrying Packet Switched (PS) domain services, conversational services and video services; and the third generation E-UTRAN system is mainly used for carrying super-speed PS domain services.
Therefore, according to the current network deployment, the mobility between the second generation GSM system and the third generation ECDMA system is very important. Moreover, in the near future, the mobility management of the third generation E-UTRA system, for example, switching to the hot spot region of the E-UTRA system, will also become important.
The switching process caused by the above mobility management among the systems requires the measurement for the target system and the target carrier frequency in the prior switching preparatory stage so as to make an accurate switching decision.
A compressed mode plays an important role in the inter-carrier frequency measurement and inter-system measurement. When the compressed mode is adopted, the terminal can measure the non-serving carrier frequencies and the carrier frequencies of other systems without any need to be configured with dual receivers. When a terminal configured with only one receiver moves from the third generation WCDMA system to the area only covered with the second generation GSM system, it can only adopt the compressed mode to perform the inter-system measurement. Likewise, the compressed mode can also be used for the terminal which moves into or out of the area covered with the multi-carrier frequencies of the third generation WCDMA system. In the compressed mode, the terminal can perform measurement of another non-serving carrier frequency without losing any data transmitted on the serving carrier frequency.
The compressed mode is defined as a transmission mode through which the data transmission will be compressed in the time domain and a transmission gap will be generated. The receiver of the terminal can tune to another carrier frequency to perform measurement by using this transmission gap.
The transmission gap is generally described and determined by a transmission gap pattern sequence. Each set of the transmission gap pattern sequence is uniquely identified by one transmission gap pattern sequence identification. Each set of the transmission gap pattern sequence can only be used for one kind of transmission gap pattern sequence measurement purpose, namely one of the measurement purposes of Frequency-Division Duplex measurement, Time-Division Duplex measurement, GSM Carrier Received Signal Strength Indication (RSSI) measurement, GSM Initial Base Station Identity Code Identification, GSM Base Station Identity Code Identification Reconfirmation, multi-carrier frequency measurement, E-UTRA measurement and so on.
As shown in FIG. 1, each set of transmission gap pattern sequence comprises two kinds of alternate transmission gap patterns, i.e. Transmission Gap Pattern 1 and Transmission Gap Pattern 2. Each kind of transmission gap pattern provides one or two transmission gaps within one transmission gap pattern length. In addition, each set of transmission gap pattern sequence also comprises a transmission gap Connection Frame Number (CFN) indicating the start/stop time of the compressed mode, and repetition times of the transmission gap pattern, etc. These parameters are all determined according to the transmission gap pattern sequence measurement purpose.
In consideration of accelerating switching process and enhancing switching reliability, especially in the area where the radio signal quality is deteriorating rapidly, it is needed to accomplish the inter-carrier frequency measurement and the inter-system measurement quickly. In this way, it means that: the later the compressed mode is started, the better it is; and the shorter the duration time of the compressed mode is, the better it is, so as to enhance the system capacity and the user throughput. Thus, it is considered to control the compressed mode between a terminal and a NodeB by the terminal. A terminal judges that the radio signal quality of a current serving cell is not good, it might be needed to perform an inter-carrier frequency measurement and an inter-system measurement to prepare for the switching to an inter-carrier frequency/inter-system adjacent cell, then the terminal starts the compressed mode and notifies the NodeB.
However, when the terminal adopts the control method above, the following conditions can not be processed.                1) When a large number of terminals appear in one cell, the available resources of the cell might not be sufficient to guarantee the Quality of Service (QoS) of all services of all terminals, thus congestion or overload is caused. A low-cost method to cope with a congested or overloaded cell is to balance the services to an adjacent cell with lower load, and this is called a load balancing mechanism. The load balancing mechanism, by way of switching a terminal from a congested or overloaded cell to an adjacent cell with lower load, achieves the purpose of balancing services to an adjacent cell with lower load.        2) Since the operator would have a service deployment tendency for different systems or different frequency points in the condition of deploying a network with multiple radio systems, for example, the second generation GSM system processes voice services, and the third generation WCDMA system processes packet domain services. Then, after a terminal accesses the radio system (access cell) from an unexpected system or frequency layer, since the services, in accordance with the bearer feature, are not placed in the expected system or frequency layer, then it is needed to place these services in a proper radio system (adjacent cell of the access cell) to bear and run in accordance with the bearer feature, and this is called a service bearer feature mechanism. Through the service bearer feature mechanism, different services can be placed in a radio system with the proper bearer feature to bear and run, for example, voice services are placed in the second generation GSM system (adjacent cell of the access cell) to bear and run, and packet domain services are placed in the third generation WCDMA system (adjacent cell of the access cell) to bear and run.        
When performing the load balancing mechanism and the service bearer feature mechanism mentioned above, it is needed to start the compressed mode to perform the inter-carrier frequency measurement and the inter-system measurement of these adjacent cells (that is, target cells to be measured), so as to prepare for the switching to an inter-carrier frequency/inter-system adjacent cell. However, at this moment, the radio signal quality measured by the terminal in the current serving cell generally is good. After all, the nature of the load balancing mechanism or the service bearer feature mechanism is that the current serving cell is congested or overloaded, just the load of the current serving cell is too high and needs to be balanced to other cells for sharing load, or to optimize and adjust the service bearer; thus the radio signal received by the terminal has no problem and the quality is good.
For this load balancing mechanism and the service bearer feature mechanism, it is also required to start the compressed mode as late as possible and keep the lasting time of the compressed mode as short as possible, so as to reduce the load of the current serving cell quickly, prevent the current serving cell from collapse and avoid influencing all services of all terminals in the current serving cell, quickly match a proper bearer object for a service and avoid low QoS and poor service experience.
However, in the conditions that the load balancing mechanism or the service bearer feature mechanism appears, the terminal can not learn the load/bearer condition of the current serving cell and the adjacent cell (the adjacent cell is the target cell to be measured) and has no idea of the optimization and adjustment policy of the service bearer, can not learn the service bearer tendency of the current access cell and the adjacent cell of the access cell (the adjacent cell is the target cell to be measured), thus the terminal can not control the start of the compressed mode, and the QoS and the system performance of the terminal are impacted.